It would be Knightfall for Batman to actually try to glide using his cape. Physics students at the University of Leicester have calculated that he wouldn't be able to survive the aerial maneuvers displayed in the movie Batman Begins:

Due to the high speeds he would be travelling, his impact with the ground would be equivalent to him being struck by a car travelling at 50 miles per hour.

David Marshall, Tom Hands, Ian Griffiths and Gareth Douglas found that the wingspan of Batman's cape -- at 4.7 metres -- is around half that used by a hang glider.

If Batman jumped from a building 150 metres high, he could glide a distance of around 350 metres -- but the problem arises as Batman's velocity increases during his descent.

His velocity would initially rise to around 68 miles per hour, before reaching a steady 50 miles per hour as he gets down to ground level -- a speed too fast for him to land safely.